Elihu thomson



(No Model.) v

E. THOMPSON.

ELECTED MAGNETIG DBVIGEQ No. 250,175. Patented Nov. 29.13%.

UNITED S'rAT s PA ENT FFICE.

nurse 'rnonson, on NEW entrain, connncrrcutr, ASSIGNOR To run AMERICANELECTRIC COMPANY, OF SAME PLAcE- E scTRo-M'AeNET -o Device.

srscrrrcn'rroiv forming part of see Patent No. 250,175, dated November29,1881.

Application flied February 9,1881. (No model.)

To all whom it may concern.- Beit kno'wn'that I, ELIHU Tnon'rsoiv, acitizen of the United States, rosidin g at New Britain, county ofHartford,"'State of Connecticut, have invented a new and usefulElectro-Magnet-ic Device, of which the following is a specitlcation'.

- The object of my invention is to obtain a greatly-increased attractiveenergy in electro. magnetic 'coils with movable cores, and also toconstruct a coil which when traversed by an electric current shall exertan axial attraction upon amovable core partially inclosed thereby, whichattraction shall be practically constantjor a constant current,independently of changes of position within certain limits.

I apply my invention to all cases where great attractive energy is to beexerted through a considerable range of position of the moving core, andwhere the tendency olfa, core to enters coil is required to be thesamcin various positions when a constant current circulates.

My invention is adapted to operate regulators for electric currents,electric-lamp mechanism, signal apparatus, &c.

Briefly, my invention consists .of a coil-of insulated conductor,through whichan electric current can be sent, surrounded by an ironcasing'and inclosing a. movable core, having certain relations to aconical extension ofiron, ssherein described.

Figure 1 is a side view of the device, where Q is a helix or coilofwire; I I, a lateral outer 'cusin g of iron P, an iron base-plate, andconical extension'l- H, a movable. iron tube or hollow eore. Fig. 2 isin all respects similar to Fig. 1, except that the parts are inverted.

Referring to Fig. 1, 0 is a coil through n hich a current of electricityis passed, which causes an axial attraction of the core, H, of iron,into the-interior of said coil; but this attractive force is very feeblewhen coil and core only are used.

My improvement consists in adding an external iron casingextendin fromthe top of the coil 0 over its sides an tothe iron. plate P. I am thusenabled to obtain from; a 'given core from four to five times themechanical energy in entering'the coil 0 as would be obtained withoutthe casing; but to further base-plate P.

improve my device and enable it to be readily adapted to its varioususes, 1 procure an attractive energy constant for the some currentstrength, notwithstanding chan geso'f position 'of the core H withrespect to the coil 0, by the introduction of an' iron extension, P,extending upward-in the center of the coil from the A central rod isattached to the. core H, by means of which its force may be transmitted.A weight, W, issoinetimes used to counterbaiancc,either'partly orentirely,

the weight of the core H. Ahrass tube, J,

surrounds the movable core H, and it is preferably filled with oil orglyccrine, in order to damp or check sudden motions of the core.

The casing need not cover the coil-(loompletely, but may consist otanymashrbf mag. netic substance serving to join and convey. the" magneticpolarization around the exterior of the coil O, and from end to endcxteriorly.

Fig. 2 shows the parts inverted, and this is sometimes aconvenientdisposition.

The object of the cone P is to compensate for the diminished axial forceof the coil 0 It is well known that when a plain iron-core is attractedinto a helix the magnetic efi'ect rises to a maximum, then falls to aminimum or zero, when the center of the coil is in the same position asthe center of the core, and various devices have been attempted toovercome this changing force and render it.more uniform. The coil itselfhas been wound tapering, the core has had various outlines given to it,counterbalancing devices I used to increaseand diminish their effectupon the core, and thus obtain uniformity of action in variouspositions;

but I do not find that by any other device than my present invention, orits manifest equivalent, powerful attractive energy and uniformattraction in'various positions have been rea'b ized, and I attribute myresults to the casing or closed magnetic circuit outside the coil opcrsting in-conjunetion with the'annular core ,H and conical extension P.The motion of the core H toward the base of the cone P brings the sidesof the cone or taper P! nearer the core H, and there results anincreased attractive force, which is greater as'the direct'axial forceof the coil 0 upon the core H is less, and

by properly shaping the parts, the variations of the one being oppositeto those of the other, a uniform tendency of the core H to move withinits coil 0 axially is produeed with the same current.

With various dimensions of parts experiment will determine the properproportions to be enrployed to obtain all the effects desired;

bit for the guidance of those skilled in the art a single example willbe given. I have made the coil live inches in length, five inchescxternal diameter, three inches internal diameter; the core H fiveinches long, two and three-fourths extt -nal diameter, and two andone-fourth internal diameter; the cone 1 two and three-fourths incheshigh, two inches wide at base, and tapering upward nearly to a point.With a casing about one-fourth inch thick an attractive forceis obtainedpractica'llyunit'orm for arange of one and one-fourth inch movement ofthe core when a constant current is flowing through the coil. Anequivalent arrangement isto provide the core H with atapering conicalextension and cut a circular opening in the base-plate I, through whichthe taper extremity of the core may pass as said core is drawn into thecoil 0. It is thus that the iron of the core gradnall y gains proximityto the base-plate and uniformity of action is obtained.

I claim as my invention---' 1. In combination with a hollow movable coreplaced in the interior of a coil of wire or helix, an external casingand tapering exten' sion connected to said casing for the purposeof'obtaining an axial attraetiveforce constantforaconstantourrent,independentlyof changes of position of said corewith respectto said coil within practicable-limits.

2. A movable core, H, surrounded by a coil of insulated wire andimmersed in avessel ofoil or glycerine, and whereby said core is checkedin its movement, in consequence of the resistance to the passage of saidoil or glycerine from a position above said core to a position below it,and vice versa.

3. The combination, in an improved electro' magnetic device, of thefollowing elements, viz: a coil or helix, a. movable core, a vessel ofoil or glycerine in which said core moves, an exterior iron casing, andtapering extension of the same interior to said coil or helix.

ELIHU THOMSON. Witnesses:

E. W. RICE, E. F. PECK.

